Accompanied with the spread of network techniques represented by the Internet, improvement in reliability for each network is a pressing need.
In recent years, reliability for a network has been improved by performing dynamic route control after preparing a redundant structure including node apparatuses and links for the network. In the network which executes the dynamic route control, the node apparatuses which form the network exchange information about connection statuses thereof. Based on such information, an optimum route is autonomously determined.
For example, if a node apparatus detects a failure in a link connected to the node apparatus or a node apparatus adjacent thereto (accordingly, a topology change) occurs, the node apparatus which detects the failure communicates the failure to other node apparatuses. Accordingly, all node apparatuses within the network perform route computation without considering the damaged node apparatus or link, so as to determine a new route.
As described above, even if a failure occurs, the dynamic route control makes it possible to continue the communication service using only the remaining node apparatuses and links.
In order to implement such dynamic route control, a standardization organization IFTF (Internet Engineering Task Force) defines standardized route control protocols such as BGP (Border Gateway Protocol)-4 (for example, see Non-Patent Document 1), OSPF (Open Shortest Path First) (for example, see Non-Patent Document 2), and RIP (Routing Information Protocol) (for example, see Non-Patent Document 3).